Question

Unity’s documentation says of the RegisterInstance<> method that registers an instance so that that particular instance is returned everytime Resolve<> is called.

However, this example below shows that each time Resolve<> is called, a new instance of the type is returned.

Why is this?

using System; using System.Windows; using Microsoft.Practices.Unity;  namespace TestUnity34 {     public partial class Window1 : Window     {         public Window1()         {             InitializeComponent();              Validator validator1 = new Validator();             IUnityContainer container = new UnityContainer();             container.RegisterInstance<IValidator>(validator1);              Validator validatorCopied = validator1;             Console.WriteLine(validator1.GetHashCode()); //14421545             Console.WriteLine(validatorCopied.GetHashCode()); //14421545              Validator validator2 = container.Resolve<Validator>();             Console.WriteLine(validator2.GetHashCode()); //35567111              Validator validator3 = container.Resolve<Validator>();             Console.WriteLine(validator3.GetHashCode()); //65066874         }     }      interface IValidator     {         void Validate();         string GetStatus();     }      public class Validator : IValidator     {         public void Validate() { }          public string GetStatus() { return 'test'; }     } } 

Answer 1

You have configured your container with IValidator so you will have to resolve using IValidator instead of Validator:

Validator validator1 = new Validator();  IUnityContainer container = new UnityContainer();  container.RegisterInstance<IValidator>(validator1);  Validator validatorCopied = validator1;  Console.WriteLine(validator1.GetHashCode()); Console.WriteLine(validatorCopied.GetHashCode()); IValidator validator2 = container.Resolve<IValidator>();             Console.WriteLine(validator2.GetHashCode());              IValidator validator3 = container.Resolve<IValidator>();             Console.WriteLine(validator3.GetHashCode());  

Alternatively you can keep your registration using Validator but then you have to resolve using Validator as well:

Validator validator1 = new Validator(); IUnityContainer container = new UnityContainer(); container.RegisterInstance<Validator>(validator1); Validator validatorCopied = validator1; Console.WriteLine(validator1.GetHashCode()); Console.WriteLine(validatorCopied.GetHashCode()); Validator validator2 = container.Resolve<Validator>(); Console.WriteLine(validator2.GetHashCode()); Validator validator3 = container.Resolve<Validator>(); Console.WriteLine(validator3.GetHashCode());